Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$239.48	6.475%	$254.9863	$254.99	$255.00	$255.00
Purchase #2	$35.80	9.842%	$39.3234	$39.32	$39.30	$39.30
Purchase #3	$112.43	12.477%	$126.4579	$126.46	$126.45	$126.50
Purchase #4	$150.36	6.712%	$160.4522	$160.45	$160.45	$160.50
Purchase #5	$168.36	13.773%	$191.5482	$191.55	$191.55	$191.50
Purchase #6	$241.37	3.570%	$249.9869	$249.99	$250.00	$250.00
Purchase #7	$66.88	8.732%	$72.72	$72.72	$72.70	$72.70
7 purchase totals =	$1,014.68		$1,095.4749	$1,095.48	$1,095.45	$1,095.50